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Up to half of patients who receive coronary angiography for suspected angina don’t have obstructive coronary artery disease (CAD). But their symptoms often persist nonetheless, and with a lack of a definitive diagnosis it’s difficult for clinicians to optimally manage their treatment.

A new study presented at TCT 2018 and published in the Journal of the American College of Cardiology represents a potential breakthrough in this regard. Using additional functional testing, researchers led by Thomas J. Ford, MBChB, effectively diagnosed microvascular and/or vasospastic angina—as well as non-cardiac related chest pain—and used that information to guide therapy decisions and significantly improve angina and quality-of-life outcomes.

“After a negative coronary angiogram, the diagnosis is often unclear and then patients leave our cath labs with diagnostic uncertainty,” Ford said in presenting the CorMicA trial results Sept. 25 at TCT in San Diego. “And where there’s an uncertain diagnosis, how can you be expected to get the treatment right?”

Patients from two cath labs in the West of Scotland were eligible for randomization if they had no obstructive disease upon angiography. Seventy-five patients had the additional diagnostic procedure while 76 underwent a sham diagnostic procedure. Nearly three-quarters (73.5 percent) of the patients in the study were women, consistent with microvascular angina being predominantly a female condition.

According to Ford, the diagnostic procedure took about 20 minutes, involved a standard guidewire, measured metrics of microvascular circulation and included a stress test to see if the small vessels were “excitable.”

Before randomization, physicians considered a possible diagnosis of angina due to coronary artery function in about 46 percent of patients in each group. But after randomization, the frequency of diagnosis related to coronary artery function was 88 percent in the intervention arm and 46.1 percent in the control arm. A missed diagnosis of microvascular and/or vasospastic angina occurred in 35.5 percent of the cases in the control group and only 2.7 percent in the intervention group.

The intervention patients were almost twice as likely to receive antianginal therapy (87.8 percent versus 48.7 percent) and nearly three times as likely to have angina therapy tailored specifically to treat coronary artery function (86.5 percent versus 30.3 percent). Their Seattle Angina Questionnaire summary scores six months later also improved by a mean 11.7 units, on a 0 to 100 scale, compared to patients who didn’t undergo the diagnostic procedure.

“This was driven by an improvement in physical limitation and an improvement in angina frequency, so these patients were feeling better with less angina after the right diagnosis was made,” Ford said. “The quality of life amongst the patients in the intervention arm was improved, and their treatment satisfaction was higher.”

David J. Cohen, MD, the director of cardiovascular research at Saint Luke’s Mid America Heart Institute in Kansas City, Missouri, pointed out the baseline Seattle Angina Questionnaire score in this study—which was around 50—was lower than in most previous trials. This means these patients were more severely symptomatic, which could be a trigger for further testing such as that conducted in this trial, Cohen said. Ford agreed.

“If someone doesn’t have troublesome symptoms then we can’t make them any better, but for patients with really disabling angina I think we do deserve to give that patient a definitive diagnosis, and our study is maybe the first to support further research in the area,” Ford said.

Ford noted there were no serious adverse events associated with the diagnostic testing. He said common minor adverse events included bradycardia and short-lived bouts of atrial fibrillation; the AFib rate in the study was 5 percent but all patients were in sinus rhythm at discharge, Ford said.

The diagnostic procedure also included adenosine, which has a reputation as being poorly tolerated by some patients. Ford said it’s important to reassure patients ahead of time any effects they’re feeling from adenosine are a transient physiological response, and that it won’t have harmful, long-term effects.

“I think the arguments on both sides are that adenosine does take time, it’s not cheap and then you can have side effects,” said Ajay J. Kirtane, MD, SM, with NewYork-Presbyterian/Columbia University Medical Center in New York. “That’s kind of the reasons why—I think the time being the most important one—that there’s been a movement towards resting indices for physiological testing but for these tests you can’t do resting indices.

“But my interpretation of these data is that for these types of patients, we should be giving adenosine. … If the adenosine is going to give (patients) a diagnosis, I bet they’d like it a lot more.”